<template>
  <div class="mark-line">
    <div
      v-for="line in lines"
      :key="line"
      class="line"
      :class="line.includes('x')? 'xline' : 'yline'"
      :ref="line"
      v-show="lineStatus[line] || false"
    ></div>
  </div>
</template>

<script>
import eventBus from '@/utils/eventBus'

export default {
  data() {
    return {
      lines: ['xt', 'xc', 'xb', 'yl', 'yc', 'yr'], // 分别对应三条横线和三条竖线
      diff: 3, // 相距 dff 像素将自动吸附
      lineStatus: {
        xt: false,
        xc: false,
        xb: false,
        yl: false,
        yc: false,
        yr: false,
      },
      editor: null,
    }
  },
  mounted() {
    this.editor = document.querySelector('#editor')
    // 监听元素移动和不移动的事件
    eventBus.$on('move', (dragNode, isDownward, isRightward) => {
      this.showLine(dragNode, isDownward, isRightward)
    })

    eventBus.$on('unmove', () => {
      this.hideLine()
    })
  },
  methods: {
    hideLine() {
      Object.keys(this.lineStatus).forEach((line) => {
        this.lineStatus[line] = false
      })
    },

    showLine(dragNode, isDownward, isRightward) {
      const lines = this.$refs
      const components = document.querySelectorAll('.shape')
      const dragNodeRectInfo = this.getNodeRelativePosition(dragNode)
      const dragNodeHalfwidth = dragNodeRectInfo.width / 2
      const dragNodeHalfHeight = dragNodeRectInfo.height / 2

      this.hideLine()
      components.forEach((node) => {
        if (node == dragNode) return
        const { top, height, bottom, left, width, right } = this.getNodeRelativePosition(node)
        const nodeHalfwidth = width / 2
        const nodeHalfHeight = height / 2

        const conditions = {
          top: [
            {
              isNearly: this.isNearly(dragNodeRectInfo.top, top),
              lineNode: lines.xt[0], // xt
              line: 'xt',
              dragShift: top,
              lineShift: top,
            },
            {
              isNearly: this.isNearly(dragNodeRectInfo.bottom, top),
              lineNode: lines.xt[0], // xt
              line: 'xt',
              dragShift: top - dragNodeRectInfo.height,
              lineShift: top,
            },
            {
              // 组件与拖拽节点的中间是否对齐
              isNearly: this.isNearly(dragNodeRectInfo.top + dragNodeHalfHeight, top + nodeHalfHeight),
              lineNode: lines.xc[0], // xc
              line: 'xc',
              dragShift: top + nodeHalfHeight - dragNodeHalfHeight,
              lineShift: top + nodeHalfHeight,
            },
            {
              isNearly: this.isNearly(dragNodeRectInfo.top, bottom),
              lineNode: lines.xb[0], // xb
              line: 'xb',
              dragShift: bottom,
              lineShift: bottom,
            },
            {
              isNearly: this.isNearly(dragNodeRectInfo.bottom, bottom),
              lineNode: lines.xb[0], // xb
              line: 'xb',
              dragShift: bottom - dragNodeRectInfo.height,
              lineShift: bottom,
            },
          ],
          left: [
            {
              isNearly: this.isNearly(dragNodeRectInfo.left, left),
              lineNode: lines.yl[0], // yl
              line: 'yl',
              dragShift: left,
              lineShift: left,
            },
            {
              isNearly: this.isNearly(dragNodeRectInfo.right, left),
              lineNode: lines.yl[0], // yl
              line: 'yl',
              dragShift: left - dragNodeRectInfo.width,
              lineShift: left,
            },
            {
              // 组件与拖拽节点的中间是否对齐
              isNearly: this.isNearly(dragNodeRectInfo.left + dragNodeHalfwidth, left + nodeHalfwidth),
              lineNode: lines.yc[0], // yc
              line: 'yc',
              dragShift: left + nodeHalfwidth - dragNodeHalfwidth,
              lineShift: left + nodeHalfwidth,
            },
            {
              isNearly: this.isNearly(dragNodeRectInfo.left, right),
              lineNode: lines.yr[0], // yr
              line: 'yr',
              dragShift: right,
              lineShift: right,
            },
            {
              isNearly: this.isNearly(dragNodeRectInfo.right, right),
              lineNode: lines.yr[0], // yr
              line: 'yr',
              dragShift: right - dragNodeRectInfo.width,
              lineShift: right,
            },
          ],
        }

        const needToShow = []
        Object.keys(conditions).forEach((key) => {
          // 遍历符合的条件并处理
          conditions[key].forEach((condition) => {
            if (!condition.isNearly) return
            // 修改当前组件位移
            this.$store.commit('setShapePosStyle', { key, value: condition.dragShift })
            condition.lineNode.style[key] = `${condition.lineShift}px`
            needToShow.push(condition.line)
          })
        })

        // 同一方向上同时显示三条线可能不太美观，因此才有了这个解决方案
        // 同一方向上的线只显示一条，例如多条横条只显示一条横线
        if (needToShow.length) {
          this.chooseTheTureLine(needToShow, isDownward, isRightward)
        }
      })
    },

    chooseTheTureLine(needToShow, isDownward, isRightward) {
      // 如果鼠标向右移动 则按从右到左的顺序显示竖线 否则按相反顺序显示
      // 如果鼠标向下移动 则按从下到上的顺序显示横线 否则按相反顺序显示
      if (isRightward) {
        if (needToShow.includes('yr')) {
          this.lineStatus.yr = true
        } else if (needToShow.includes('yc')) {
          this.lineStatus.yc = true
        } else if (needToShow.includes('yl')) {
          this.lineStatus.yl = true
        }
      } else {
        // eslint-disable-next-line no-lonely-if
        if (needToShow.includes('yl')) {
          this.lineStatus.yl = true
        } else if (needToShow.includes('yc')) {
          this.lineStatus.yc = true
        } else if (needToShow.includes('yr')) {
          this.lineStatus.yr = true
        }
      }

      if (isDownward) {
        if (needToShow.includes('xb')) {
          this.lineStatus.xb = true
        } else if (needToShow.includes('xc')) {
          this.lineStatus.xc = true
        } else if (needToShow.includes('xt')) {
          this.lineStatus.xt = true
        }
      } else {
        // eslint-disable-next-line no-lonely-if
        if (needToShow.includes('xt')) {
          this.lineStatus.xt = true
        } else if (needToShow.includes('xc')) {
          this.lineStatus.xc = true
        } else if (needToShow.includes('xb')) {
          this.lineStatus.xb = true
        }
      }
    },

    isNearly(dragValue, targetValue) {
      return Math.abs(dragValue - targetValue) <= this.diff
    },

    // 获取节点相对编辑器的位置
    getNodeRelativePosition(node) {
      let { top, height, bottom, left, width, right } = node.getBoundingClientRect()
      const editorRectInfo = this.editor.getBoundingClientRect()

      left -= editorRectInfo.left
      top -= editorRectInfo.top
      right -= editorRectInfo.left
      bottom -= editorRectInfo.top

      return { top, height, bottom, left, width, right }
    },
  },
}
</script>

<style lang="less" scoped>
.mark-line {
  height: 100%;
  //   background-color: #001d71;
}
.line {
  background: #59c7f9;
  position: absolute;
  z-index: 1000;
}
.xline {
  width: 100%;
  height: 1px;
}
.yline {
  width: 1px;
  height: 100%;
}
</style>